- Remove the section-header ➕ "add landing page" button; landing pages are
now created via the page editor pen.
- Treat saving a page with empty (after stripping) Markdown as deleting it:
childless nodes are removed, nodes with children become content-less labels.
- Restrict server-side slugs to [a-z0-9_-] with no leading underscore or dot;
drop the reserved-filename blacklist.
- Render placeholder pages for content-less category labels and link them to
their first published child in the navigation.
- Make task-list checkboxes live, non-disabled inputs: toggling updates the
Markdown source, updates the open CodeMirror document when the page editor is
open, and persists to the server when no editor is open. Errors revert the UI.
- Update docs and AGENTS.md conventions accordingly.